Apparatus for adjusting spring tensions



G RNG TENSIDNS US ADJUST? Patented Oct. 24, 1950 't APPARATUS' Foa ADJUs'rING SPRING TENsIoNs Charles H. Trimble, Baltimore, Md., assigner to Western Electric Company, Incorporated, New York, N .A Y., a corporation of New York Application April 16, 1948, Serial No. 21,496

" `s Claims. (C1. 15s-4s) This invention relates to apparatus for adjusting spring tensions, and more particularly to apparatus for adjusting tension of leaf springs.

In the manufacture of leaf springs, such as jack 4Spring contacts used in the telephone industry, it is essential that the springs have a predetermined amount of reactive force when they are moved to a predetermined operating position. In some instances the springs are too weak when moved to such a position and must be bent beyond their elastic limit a predetermined amount in order to provide Sufficient reactive force when they are moved to that position. Such weak springs also vary in strength from each other and, hence, must be bent different amounts to secure the desired reactive force for the operating position. In the past there has been no satisfactory apparatus for bending springs the correct amount to increase their reactive force to a predetermined amountV for the operating positionA thereof.

An object of the invention is to provide newv and improved apparatus for adjusting spring tensions.

A further object of the invention is to provide new and improved apparatus for adjusting the tension of a leaf spring to an extent proportional to the variance of the unadjusted leaf spring tension with respect to optimum leaf spring tenslon.

An apparatus illustrating certain features of the invention may include a feeler for iiexing a leaf spring, means for bending the leaf spring beyond its elastic limit, means for driving the spring-bending means, and means responsive to the feeler for varying the force of the driving means in inverse proportion to the reactive force of the spring for a predetermined flexed position.

A complete understanding of the invention may be obtained from the following detailed description of an apparatus forming a specific embodiment thereof, when read in conjunction with the appended drawing, in which:

Fig. 1 is a fragmentary elevation of an apparatus forming one embodiment of the invention with portions thereof broken away, and

Fig. 2 is a schematic view of part ofthe ap paratus shown in Fig. 1. y

Referring now in detail to the drawing, a jack spring III, which is to be adjusted,if necessary, to provide a predetermined reactive force when in a predetermined position designated its operating position, is clamped between jaws I 4-I4, which are held together by a-bolt I6. A frame I8 Y 2 mounted pivotally on a rod 28 secured to a bracket 22 is swungin a counterclockwise direction, as viewed in Figi, against the action of a spring 24. The frame I8 is swung away from'a stop 26 secured to the bracket 22 toward a position in which the frame engages a fixed stop 28. As the frameis so swung, a one-way trip 30, which is normally held against a stop 32, is moved past a lever 34 on a limit switch 36 secured to the bracket 22 without actuating the limit switch.

Prior to the engagement of the frame I8 with the stop 28, a feeler 40 mounted Slidably in a guide 42 carried by the frame engages the jack spring I8 and presses the spring I0 downwardly, as viewed in Fig. l. The spring IIJ reacts against the feeler 4U and pushes it upwardly in the guide 42 against the action of a compression spring 44 until equilibrium is reached as the frame I8 strikes the stop 28. As the frame I8 strikes the stop 28, an arm 48 of a bellcrank lever 50 strikes an adjustment screw 52 secured to the bracket 22. The bellcrank lever 5I) is mounted pivotally on a pin 54 secured to the frame I8, and is moved by the adjustment screw 52 to an overcenter position with respect to the pin 54. An overcenter spring 56 secured to the arm 48 and to the frame I8 then swings the lever 50 in a counterclockwise direction. As the lever E'is so swung, an arm 58 thereof, having a slot 68 in an end thereof, moves a toothed latch 62 to the left, as viewed in Fig. 1, along a guideway 66 carried by the frame I8. The latch 62 is moved into engagement with ratchet teeth 68 formed on the feeler` 40 to hold the feeler 4D in the position to which itis moved by the jack spring I in reaching equilibrium.

AS the feeler 40 is moved upwardly with respect to the frame I8 by the jack spring III, it swings a lever I0 in a clockwise direction. The lever 'I0 is mounted pivotally on a pin 'I2 carried by the feeler 40 and is provided with a slot 14, and a pin I6 secured to the guide 42 Aextends into the slot I4. A grounded contacter I8 carried by the lever 'I0 engagesy aV resistance wire 80 of a potentiometer resistance unit 82 mounted in a housing 84. The housing 84 is provided with an arcuate slot 86 throughV which the contactor 'I8 projects to engage the resistance wire 80. Movement of the feeler 4U upwardly in the guide 42 moves the Vcontactori upwardly along the V resistance wire BI) to draw more of the resistance wire in series with the lswitch 36, a winding 90'y of a solenoid 92 positioned below the jack spring IU and a battery 94.

After the frame I8 has been moved against the stop 28,5it is swung in a clockwise direction, as

viewed in Fig. l, toward the stop 26. This moves the feeler 40 out of engagement with the jack spring l0, and the trip 30 momentarily engages the arm 34 of the switch 36 to close this switch momentarily. The momentary closing of the switch 36 closes a circuit through ground, the battery 94, the solenoid winding 90, the switch 36, the portion of the resistance wire 80 between the contacter 'i8 and the winding 90, the contactor 'I8 and ground, and current flows through the solenoid winding 90. An armature 96 of the solenoid 92 is drawn upwardly by magnetic iiux induced by the current which passes through the winding 90 and strikes the jack spring I0 to bend the jack spring Ii) beyond its elastic limit, thereby increasing the reactive force within its elastic limit of the spring I for its operating position,

As the trip moves beyond the arm 34, the switch 36 is reopened, and the armature S6 moves back to its normal position. As the frame |8 i comes into engagement with ,the stop 28, after the switch 36 has been closed and reopened, the arm 48 of the lever 50 strikes an adjustment stop |00 secured to the bracket 22 and is moved in a clockwise direction, as viewed in Fig. 1. The stop r.

|00 moves the lever 58 to an overcenter position with respect to the overcenter spring 56 and the pin 54, and the spring 56 continues to pull the lever in a clockwise direction until it is restrained by a collar |02 secured to the latch 62 striking a shoulder |04 formed in the guide 66. By then the latch 62 has been moved out of engagement with the feeler 40, and the compression spring 44 moves the feeler 40 to its normal position, in which position a collar |06 abuts a bushing |08 carried by the guide 42.

Operation In the operation of the apparatus described hereinabove, the frame I8 is swung in a counterclockwise direction, as viewed in Fig. 1, to a position in which the frame engages the stop-28. As the frame I8 approaches this position, the feeler 40 engages the jack spring I0, and as the frame is moved farther into engagement with the stop 28, the feeler flexes the spring |0 in proportion to the reactive force of the spring. The reactive force of the spring I0 moves the feeler upwardly in the guide 42 in proportion to the resistance of the spring I0, and the feeler through thelever I0 moves the contacter 18 along the resistance wire in proportion to the resistance of the spring I0. Just as the feeler 40 and the contactor 18 reach their adjusted positions, the arm 48 of the bellcrank lever 50 strikes the stop 52. The overcenter spring 56 then actuates the latch 62 through the bellcrank lever to latch the feeler and the contactor in these positions.

The frame I8 is then swung in a clockwise direction, as viewed in Fig. 1, to move sequentially the feeler away from the jack spring I0 and the one-way trip 30 into and out of engagement with the arm 34 of the switch 36 to momentarily close the switch to actuate the solenoid 92 while the feeler 40 and the contactor I8 are held in their adjusted positions. The armature 96 of the solenoid engages the jack spring 0 with a force proportional to the current owing through the winding -of the solenoid, and this current is inversely proportional to the amount of resistance in series with the winding 90 so that the bending force onl the spring from the armature is inversely proportional to the reactive force of the spring on the feeler 40 as the feeler adjustment is made. Thus, if force of the spring |0 is suciently high for its operating position, it will throw all of the resistance 80 into series with the winding 90 to limit severely the current through the winding 90, thereby reducing the impact force of the armature 96 to a negligible value. However, if the force of the spring I0 in its operating position is low the spring will not adjust the feeler 4D to out out any appreciable amount of the resistance 80 and the impact force of the armature 96 will then be high to bend the spring |0 suii'ciently beyond its elastic limit that it will have the required' reactive force, still within its elastic limit, for the operating position of the spring.

After the switch 36 is closed and reopened as the one-way trip 30 moves past the switch, the arm 48 of the bellcrank lever 50 strikes the adjustment stop |00, and the overcenter spring 56 actuates the bellcrank lever to move the latch 62 out of engagement with the feeler 40. The spring 44 then moves the feeler to its unadjusted position, and the contacter 18 is moved to the zero end of the resistance wire 80. The frame i8 comes to a position of rest against the stop 26 just as the bellcrank lever 50 is moved overcenter by the adjustment stop |00.

The apparatus described hereinabove automatically varies the bending force applied to the jack spring I0 in accordance with the reactive force of the spring I0 for a particular position of the feeler 40 so that cut and try methods of adjusting the reactive force of the spring for its operating position are avoided.

What is claimed is:

1. An apparatus for adjusting spring tension, which comprises a feeler, means for holding a spring under stress against the feeler, means for mounting the eeler resiliently, whereby the resiliently mounted feeler is moved relative to the feeler-mounting means in proportion to the reactive force of the spring, means for applying a bending force to the spring, and means responsive to the position of the feeler with respect to the feeler-mounting means for adjusting the force-applying means to vary the force of the force-applying means.

2. An apparatus for adjusting spring tension, which comprises a feeler, means for holding a spring in a predetermined position, means for mounting the feeler resiliently, means for moving the feeler-mounting means to a predetermined position to move the feeler into engagement with the spring, wherebythe spring is flexed and the resiliently mounted feeler is moved relative to the feeler-mounting means in proportion to the reactive force of the spring, means for latching the feeler in an adjusted position with respect to the feeler-mounting means, said feeler-mounting means being removable away from the spring to' move the feeler away from the spring, means for applying a force to the spring to bend it beyond f its elastic limit, and means responsive to movement of the feeler with respect to the feelermounting means for adjusting the force-applying means to vary the force of the force-applying means.

3. An apparatus for adjusting spring tension, which comprises a device for calibrating the tension of a jack spring, a solenoid actuatedV hammer for bending jack springs, a variable resistance in-series with the winding of the solenoid, a feeler for engaging a jack spring, and means operable by the feeler for controlling the variable resistance to vary the resistance placed in series with the solenoid winding.

4. An apparatus for adjusting spring tension, which comprises a clamp for holding a spring, a solenoid including an armature for engaging the spring when the solenoid is actuated, a feeler for engaging the spring and responsive to the reactive force of the spring, and means responsive to the reactive force on the feeler for applying a voltage inversely proportional to the reactive force of the spring to the solenoid winding.

5. An apparatus for adjusting spring tension, which comprises a solenoid including an armature and a winding, a clamp for holding a spring in the path of movement of the armature of the solenoid, a frame movable toward and away from a spring held by the clamp, a stop for limiting movement of the frame toward the spring, a feeler mounted on the frame, means for urging the feeler toward the spring, a resistance in series with the solenoid winding, means for adjusting the variable resistance, means for applying a constant voltage to the variable resistance between one side of the variable resistance and one side of the solenoid winding, and means responsive to the reactive force of the spring on the feeler for actuating the resistance-adjusting means to Vary the portion of the resistance in series with the solenoid winding in proportion to the magnitude of the reactive force on the feeler.

6. An apparatus for adjusting spring tension, which comprises a solenoid including a solenoid winding and an armature, means for positioning a spring in the path of movement of the armature of the solenoid, a feeler, a frame for mounting the feeler movably thereon and for moving the feeler into engagement with the spring, means for urging the feeler toward the spring and for permitting the feeler tol be moved relative to the frame by the reactive force of the spring, a stop for limiting the movement of the frame toward the feeler, means for latching the feeler in a position in which it is moved as the frame is moved against the stop, a resistance winding in series with the solenoid winding a contactor for engaging the resistance wire, means operable by movement of the ieeler with respect to the frame for moving the contactor along the resistance wire, a source of current in series with the contactor and the solenoid winding, and a switch for closing the circuit including the source of current, the contactor and the portion of the resistance wire between the contactor and the solenoid winding and the solenoid winding, whereby the solenoid armature is moved against the spring.

7. An apparatus for adjusting spring tension, which comprises a clam'p for holding a jack spring in a predetermined position, a solenoid including a solenoid winding and an armature positioned in alignment with a spring held by the clamp, a frame, a stop for limiting movement of the frame toward the spring, a feeler mounted slidably on said end of the frame for engaging the spring, means for urging the feeler toward the spring, a resistance wire carried by a frame having one end thereof connected in series to one end of the solenoid winding, a contactor movable over the resistance wire, amplifying means responsive to movement of the feeler with respect to the frame for moving the contactor with respect to the resistance wire when the feeler is moved with respect to the frame, and means for applying a source of constant potential to the contactor and the other side of the solenoid winding.

8. An apparatus for adjusting spring tension, which comprises a clamp for holding a spring in a predetermined position, a solenoid including a solenoid winding in an armature positioned in alignment with a spring held by the clamp, a frame having one end thereof pivotally mounted for movement toward the spring, a stop for limiting movement of said end of the frame toward the spring, a feeler mounted slidably on said end of the frame for engaging the spring, means for urging the feeler toward the spring, a resistance winding carried by a frame having one end thereof connected in series to one end of the solenoid winding, a contactor movable over the resistance wire, a lever connected to the contactor and to the feeler for moving the contactor with respect vto the resistance wire when the feeler is moved with respect to the frame, an overcenter latch carried by the frame, a stop for actuating the overcenter latch when the frame strikes the stop to latch the feeler in the position in which it is moved with respect to the frame by the reactive force of the spring, a source of constant potential connected to the contactor and the other side of the solenoid winding, a switch connected in series with the solenoid, the contactor, the resistance wire and the source of current, means for actuating the switch momentarily when said end of the frame is swung away from the spring to close the switch, wh-ereby the solenoid armature is moved against the spring with a force inversely proportional to the reactive force of the spring,

and means for actuating the overcenter latch to release the feeler. l

CHARLES H. TRIMBLE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,355,468 Robb Aug. 8, 1944 2,364,989 Mallina Dec. 12. 1944 

